CRT may be considered for patients with chronic RV pacing or who are likely to be chronically paced, have signs and/or symptoms of heart failure, and a LVEF value ≤ 35% (Recommendation Weak, Quality Low).

Values and Preferences This recommendation places great value on the inclusion criteria of the landmark trials and the characteristics of the patients enrolled.

Practical Tip Attempts to minimize RV pacing, when implemented, should be undertaken before consideration of CRT upgrade. There is less evidence for the utility of CRT in patients who do not have a pre-existing LBBB and are chronically RV-paced. The risks of CRT upgrade need to be considered and balanced with the potential benefits of CRT upgrade. Patients undergoing AV junctional ablation with moderate LV dysfunction might benefit from CRT, as may those who have an indication for chronic pacing and characteristics similar to patients randomized in BLOCK HF. It is often difficult to predict reliably which patients will be chronically RV paced at the time of initiation of pacemaker therapy.